JP2006032132A - Powder material for air electrode of solid oxide fuel cell, air electrode, and solid oxide fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air electrode raw material powder capable of miniaturizing an air electrode structure for realizing high performance of an air electrode of a solid oxide fuel cell.
SOLUTION: It is represented by the general formula ABO ₃ , and A is composed of one or more elements selected from the group of La and rare earth elements, and one or more elements selected from the group of Sr, Ca, and Ba, and B Is a perovskite composite oxide powder composed of one or more elements selected from the group consisting of Mn, Co, Fe, Ni and Cu, having an average particle size of 1 μm or less and a width of the particle size distribution within a predetermined range Is limited to.
[Selection] Figure 1

Description

  The present invention relates to an air electrode raw material powder for a solid oxide fuel cell, an air electrode produced using the air electrode raw material powder, and a solid oxide fuel cell including the air electrode.

  In order to reduce the temperature of the solid oxide fuel cell (hereinafter abbreviated as “SOFC” where appropriate) (for example, 700 ° C. or lower), it is necessary to improve the performance of the air electrode. Control of the fine structure of the air electrode is indispensable.

In general, the SOFC air electrode material includes (La _1-x Sr _x ) MnO ₃ (lanthanum strontium manganese oxide) series and (La _1-x Sr _x ) (Co _1-y Fe _y ) O ₃ ( Perovskite complex oxides such as lanthanum strontium cobalt iron oxide) have been used, and the elemental components and composition ratios of these complex oxides have been the main development targets, but as shown below, the air electrode Development is also underway for structural control.

In Patent Document 1, for the purpose of reducing the polarization at the air electrode, a slurry-like perovskite complex oxide having a particle size (average particle size) of 1 μm or less is applied and fired on a zirconia sintered body (electrolyte). A solid oxide fuel cell in which an air electrode is formed is described.
In Patent Document 2, an average pore diameter is 1.0 to 5.0 μm and an average crystal grain diameter is 3.0 to 25.0 μm in order to realize output stabilization by suppressing contraction of the air electrode during operation. In addition, a solid oxide fuel cell having an air electrode made of a perovskite complex oxide having an open porosity of 20 to 45% is described, and further, an average crystal of a sintered body is obtained by pulverizing the raw material powder of the air electrode A method is described in which the particle size is adjusted to a particle size equivalent to the particle size, and this is molded and fired to form the air electrode having the above structure.

In Patent Documents 3 and 4, in order to provide an air electrode having small polarization and high long-term stability even under low temperature conditions, perovskite-type composite oxide particles having an average particle diameter of 1 to 10 μm and an average surrounding this particle are disclosed. A solid oxide fuel cell comprising an air electrode composed of cerium oxide particles having a particle size of 0.1 to 2 μm and a porosity of 20 to 50% is described. Specifically, a mixed slurry produced by adding Ce (cerium) octylate to (Pr _1-x Sr _x ) MnO ₃ (praseodymium strontium manganese oxide) powder classified to an average particle diameter of 2 to 3 μm The decomposed and polycondensed product is printed and fired on the electrolyte layer to form an air electrode in which 3 to 4 μm of Mn-based perovskite complex oxide particles are surrounded by about 1 μm of cerium-based material. .

Japanese Patent No. 2592070 Japanese Patent No. 3359212 JP 11-2114014 A JP 2000-260436 A

Among the above prior arts, Patent Document 1 describes that the particle size (average particle size) of the perovskite complex oxide particles is reduced to 1 μm or less to reduce the polarization of the solid oxide fuel cell. . However, simply reducing the particle size (average particle size) is insufficient to refine the air electrode structure, and there is a limit to improving the air electrode performance.
In Patent Document 2, the average crystal grain size is relatively large as 3.0 μm or more, and the relationship between the air electrode structure and polarization is not particularly described.
In Patent Documents 3 and 4, since the cerium-based material of about 1 μm surrounds the Mn-based perovskite complex oxide particles of 3 to 4 μm, the constituent particle diameter is relatively large, and the air electrode structure is miniaturized. It is insufficient.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an air electrode raw material powder capable of miniaturizing the air electrode structure for realizing high performance of the air electrode, and the air. An object of the present invention is to provide an air electrode and a solid oxide fuel cell produced using an electrode raw material powder.

In order to achieve the above object, the first characteristic configuration of the air electrode raw material powder of the solid oxide fuel cell according to the present invention is represented by the general formula ABO ₃ , wherein A is selected from the group of La (lanthanum) and rare earth elements And one or more elements selected from the group consisting of Sr (strontium), Ca (calcium) and Ba (barium), and B is Mn (manganese), Co (cobalt), Fe ( Iron), Ni (nickel), and Cu (copper), a perovskite composite oxide powder composed of one or more elements, having an average particle size of 1 μm or less and a predetermined particle size distribution width. The point is limited within the range.

When the average particle size of the perovskite complex oxide powder having the above composition is as small as 1 μm or less, the contact area with air increases when the powder is formed on the air electrode, and oxygen in the air is easily taken in, and oxygen The passage of ions to the solid electrolyte increases, the electrode reaction is activated, and high air electrode performance is expected.
At the same time, by restricting the width of the particle size distribution within a predetermined range, it is possible to avoid deterioration in air electrode performance due to non-uniform electrode structure when the perovskite composite oxide powder is fired to form the air electrode. Is possible. That is, when the firing temperature is set to an optimum temperature for particles having an average particle size, if the width of the particle size distribution is not limited within a predetermined range, the particles having a large particle size have poor sinterability and the particles Bonding between the two becomes weak, while particles having a small particle size tend to be sintered too much and become dense, and as a result, the non-uniformity of the electrode structure increases and the air electrode performance decreases. According to the present invention, it is possible to limit the width of the particle size distribution to a range in which the non-uniformity of the air electrode structure due to the difference in sinterability with respect to each powder particle as described above is suppressed.

  Accordingly, there is provided an air electrode raw material powder for a solid oxide fuel cell capable of miniaturizing and homogenizing the air electrode structure which is indispensable for realizing high performance of the air electrode.

In the second characteristic configuration, as the width of the particle size distribution, the ratio D ₉₀ / D ₁₀ of the cumulative volume 90% equivalent diameter D ₉₀ and the cumulative volume 10% equivalent diameter D ₁₀ is limited to a value smaller than a predetermined value, Alternatively, the ratio D ₉₀ / D _{50 of} the cumulative volume 90% equivalent diameter D ₉₀ and the cumulative volume 50% equivalent diameter D ₅₀ is smaller than a predetermined value, and the cumulative volume 50% equivalent diameter D ₅₀ and the cumulative volume 10% equivalent diameter D ₁₀ The ratio D ₅₀ / D ₁₀ is limited to a value smaller than a predetermined value.

That is, the cumulative volume 90% equivalent diameter D ₉₀ which is an index on the larger particle size side in the particle size distribution and the cumulative volume 10% equivalent diameter D ₁₀ which is an index on the smaller particle size side are measured, and the ratio D ₉₀ / by a simple process of limiting the D ₁₀ to a value smaller than the predetermined value, it can be limited to a desired width of the particle size distribution.
Alternatively, the cumulative volume 50% equivalent diameter D ₅₀ corresponding to the average particle diameter in the particle size distribution, the cumulative volume 90% equivalent diameter D ₉₀ which is a large index, and the cumulative volume 10% which is a small particle diameter index equivalent measured diameter _{D 10,} the ratio _D 90 _{/ D 50} ratio of cumulative volume of 90% equivalent diameter _{D 90} and 10% cumulative volume equivalent diameter _{D 10} for cumulative volume of 50% equivalent diameter _{D 50,} the D 50 _{/ D 10} By a simple process of limiting to a value smaller than the predetermined value, it is possible to limit the width of a desired particle size distribution. In this case, it is possible to define more accurately than when the width of the particle size distribution is defined by the ratio D ₉₀ / D ₁₀ of the cumulative volume 90% equivalent diameter D ₉₀ and the cumulative volume 10% equivalent diameter D ₁₀ .

  Accordingly, there is provided a means for simply and accurately defining the limit of the width of the particle size distribution with respect to the air electrode raw material powder of the solid oxide fuel cell capable of miniaturizing the air electrode structure.

The third characteristic configuration is that the average particle size of the perovskite complex oxide powder is 0.6 μm or less.
That is, when the average particle size of the perovskite composite oxide powder having the above composition is further reduced to 0.6 μm or less, the oxygen uptake performance in the air is increased, the oxygen ion passage is increased, and the air electrode performance is further improved. .
Accordingly, an air electrode raw material powder that can be expected to further improve the air electrode performance is obtained.

  The fourth characteristic configuration is that at least one of a stabilized zirconia powder and a dope ceria powder is homogeneously mixed with the perovskite composite oxide powder.

That is, when the stabilized zirconia powder and / or dope ceria powder are homogeneously mixed with the uniform perovskite complex oxide powder with a limited particle size distribution as described above and few extremely coarse particles and fine particles. , There is little variation in composition and structure depending on the location inside the electrode, high uniformity and higher performance air electrode can be obtained, oxygen ion conduction characteristics can be improved, and adhesion between the electrolyte and air electrode can be improved It is possible to further improve the effect of reducing the above.
Therefore, the air electrode raw material powder of the solid oxide fuel cell having further excellent electrode characteristics can be obtained.

  The fifth characteristic configuration is that the perovskite composite oxide powder is coated with at least one of stabilized zirconia powder and dope ceria powder finer than the perovskite composite oxide powder.

That is, as described above, the perovskite composite is finer in the stabilized zirconia powder and / or dope ceria powder than the uniform perovskite composite oxide powder in which the particle size distribution is limited and there are few extremely coarse particles and fine particles. When the oxide powder is coated, there is little variation in composition and structure depending on the location inside the electrode, a highly uniform air electrode with higher uniformity is obtained, oxygen ion conduction characteristics are improved, and the electrolyte / air electrode is bonded. The effect of reducing the interfacial resistance by improving the properties can be further improved.
Therefore, the air electrode raw material powder of the solid oxide fuel cell having further excellent electrode characteristics can be obtained.

The characteristic configuration of the air electrode of the solid oxide fuel cell according to the present invention is produced by molding and firing the air electrode raw material powder of any one of the first to fifth characteristic configurations, and the average particle size of the constituent particles is 1.0 μm or less, and the width of the particle size distribution is limited to a range in which the ratio D ₉₀ / D ₁₀ of the cumulative volume 90% equivalent diameter D ₉₀ and the cumulative volume 10% equivalent diameter D ₁₀ is smaller than a predetermined value, or The ratio D ₉₀ / D ₅₀ between the cumulative volume 90% equivalent diameter D ₉₀ and the cumulative volume 50% equivalent diameter D ₅₀ is smaller than a predetermined value, and the cumulative volume 50% equivalent diameter D ₅₀ and the cumulative volume 10% equivalent diameter D ₁₀ The ratio D ₅₀ / D ₁₀ is limited to a range smaller than a predetermined value.

That is, when the average particle diameter of the constituent particles of the air electrode is 1.0 μm or less, the oxygen uptake performance of the air electrode is increased, the oxygen ion passage is increased, the electrode reaction is activated, and the polarization value is reduced. High performance of cathode performance is realized.
At the same time, the ratio D of the cumulative volume 90% equivalent diameter D ₉₀ which is an index on the larger particle size side in the particle size distribution of the constituent particles of the air electrode and the cumulative volume 10% equivalent diameter D ₁₀ which is an index on the smaller particle size side. or _{90 /} D ₁₀ is limited to a value smaller than the predetermined value, or an average particle diameter in the cumulative volume of 90% equivalent diameter D ₉₀ is an indication of larger side and the cumulative volume of 50% equivalent diameter D ₅₀ corresponding the ratio _D 90 _{/ D 50} ratio, and an average of 50% cumulative volume corresponding to particle diameter equivalent diameter _{D 50} and the ratio _D 50 _{/ D 10} of the 10% cumulative volume equivalent diameter _{D 10} is an indication of particle size smaller side Are limited to a value smaller than a predetermined value, so that each particle of the air electrode raw material powder having the same limited particle size distribution maintains its particle size distribution characteristics, thereby making the electrode structure non-uniform. It is fired under proper firing conditions that do not cause it to occur.
Accordingly, an air electrode of a solid oxide fuel cell is provided in which the particle size distribution characteristic of the air electrode raw material powder is maintained and the performance deterioration due to the non-uniformity of the electrode structure is avoided.

  The characteristic configuration of the solid oxide fuel cell according to the present invention is that the air electrode having the above-described characteristic configuration is formed on one surface of the solid electrolyte and the fuel electrode is formed on the other surface of the solid electrolyte.

  That is, by adopting an air electrode that achieves high performance by miniaturizing the electrode structure as described above, a solid oxide fuel cell with low polarization and improved battery performance even under low temperature operation is provided.

  Embodiments of an air electrode raw material powder of a solid oxide fuel cell according to the present invention and an air electrode produced using the air electrode raw material powder will be described below with reference to the drawings.

The air electrode raw material powder according to the present invention is represented by the general formula ABO ₃ , wherein A is one or more elements selected from the group of La (lanthanum) and rare earth elements, Sr (strontium), Ca (calcium) and 1 or more elements selected from the group of Ba (barium), and B is selected from the group of Mn (manganese), Co (cobalt), Fe (iron), Ni (nickel) and Cu (copper) It is a perovskite complex oxide powder composed of two or more elements, has an average particle diameter of 1 μm or less, and the width of the particle size distribution is limited to a predetermined range as described later. Specifically, the average particle diameter is 0.6 μm or less.

FIG. 1 is a graph showing an example of the particle size distribution of the air electrode raw material powder in which the composition of the perovskite complex oxide is La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ . In addition, Table 1 shows numerical data such as the particle size distribution, BET value, particle size distribution in the state of being formed on the electrode, and polarization voltage value of the air electrode raw material powder. In addition, Example 1 and Comparative Example 1 are manufactured by using different manufacturing processes as described later using the same raw material.

  The particle size in the powder state was measured by a laser diffraction scattering method. The particle size in the electrode state was measured by enlarging the image of the SEM photograph and directly reading the actual particle length from the image. Further, the polarization voltage (electrode overvoltage) was measured by a current interrupt method after forming the powders of Example 1 and Comparative Example 1 on the air electrode under the same firing conditions. Each measuring instrument and measuring method are described below.

[Particle size distribution of powder]
Model: Nikkiso Co., Ltd. Microtrac particle size distribution analyzer 9320HRA (X-100)
[SEM]
Model: S-3500N manufactured by Hitachi, Ltd.
[Current interrupt method]
In this method, the current flowing between the electrodes of the SOFC during power generation is instantaneously cut, and from the voltage change between the electrodes at that time, the electrochemical polarization value (overvoltage) of the electrode indicating the electrode performance is determined as the voltage due to the battery internal resistance. It is a method of obtaining separately. That is, since the electrochemical reaction that occurs at the electrode during power generation is a reaction involving ions, the change in voltage between the electrodes is expressed as a capacitive component when the current is interrupted. On the other hand, the voltage due to the battery internal resistance changes instantaneously due to the entanglement of electrons, so this voltage change is monitored with an oscilloscope, etc., to separate the electrode overvoltage and the voltage due to the internal resistance, and Electrode performance can be evaluated by overvoltage. Therefore, the smaller the polarization value (overvoltage) ηc, the higher the performance of the electrode.

  The air electrode raw material powder of the present invention may be only the perovskite composite oxide. However, as shown in Examples 2 and 3 to be described later, the perovskite composite oxide is mixed with stabilized zirconia (for example, YSZ, YbSZ, ScSZ, Hereinafter the same) powder and dope ceria (for example, SDC, GDC, YDC, the same shall apply hereinafter) powder, or a mixture of at least one of the perovskite composite oxide powder and the perovskite composite oxide powder. Alternatively, at least one of the fine stabilized zirconia powder and the dope ceria powder may be coated.

  Next, examples and comparative examples of the air electrode raw material powder, the air electrode, and the solid oxide fuel cell according to the present invention will be described. Refer to FIG. 3 for the manufacturing process diagram of the air electrode raw material powder, the air electrode, and the solid oxide fuel cell. Further, Table 2 shows data of Examples 2 and 3 other than Example 1 and Comparative Examples 2, 3 and 4 other than Comparative Example 1.

In Example 1, an air electrode raw material powder was produced by the following steps (1) to (6).
(1) Using nitrates of La, Sr, Co, and Fe as starting materials, adjusting to a ratio of La0.6Sr0.4Co0.2Fe0.8 and dissolving in water.
(2) Using NH ₄ OH as a neutralizing agent, a salt containing each element is coprecipitated from the above solution.
(3) The obtained coprecipitated salt is washed with water and dried at 80 ° C.
(4) Further, calcination is performed at 1000 ° C. for 5 hours.
(5) The calcined product was wet-pulverized for 3 hours using an Aquamizer (rotation speed: 250 rpm) manufactured by Hosokawa Micron Corporation, and then dried.
(6) Coarse particles were removed from the dried product using a jet mill manufactured by Hosokawa Micron Corporation (classification rotation speed: 22000 rpm, pressure air amount: 0.72 Nm ³ / min) to obtain an LSCF cathode raw material powder. Here, LSCF the _{(La 1-x Sr x)} (Co 1-y Fe y) O 3 substantially, the cathode is the meaning of the air electrode. The particle size of the obtained powder is as shown in the powder column of Example 1 in Table 1.

Comparative Example 1 is different from Example 1 in that a calcined product is obtained by the steps (1) to (4) and then pulverized for 12 hours using a wet ball mill. The particle size of the obtained powder is as shown in the powder column of Comparative Example 1 in Table 1.
In Comparative Example 2, a calcined product is obtained by the steps (1) to (4) in the same manner as in Example 1, and then pulverized for 48 hours using a wet ball mill. The particle size of the obtained powder is as shown in the column of Comparative Example 2 in Table 2.

In Example 2, the LSCF powder produced in Example 1 was used as a mother particle, and SDC (Samaria doped ceria) particles (particle size: D ₁₀ = 0.169 μm, D ₅₀ = 0.26 μm, D ₉₀ = 0.554 μm) was mixed at a mixing ratio of 70/30 vol%, and homogenous mixing treatment was performed using a cyclomix manufactured by Hosokawa Micron Corporation (rotation speed: 800 rpm, treatment time: 30 min). The particle size of the obtained powder is as shown in the column of Example 2 in Table 2.

  Comparative Example 3 is different from Example 2 in that the LSCF powder produced in Comparative Example 1 is used as a base particle, and SDC particles (particle size is the same as in Example 2) are mixed at a mixing ratio of 70/30 vol%. Using a cyclomix manufactured by Hosokawa Micron Co., Ltd. (conditions are the same as in Example 2), a homogeneous mixing process was performed. The particle size of the obtained powder is as shown in the column of Comparative Example 3 in Table 2.

  In Example 3, the LSCF powder produced in Example 1 was used as a base particle, and SDC particles (particle size is the same as in Example 2) were mixed with this so that the mixing ratio was 70/30 vol%. The composite treatment was performed using Nobilta manufactured by Co., Ltd. (rotation speed: 4000 rpm, treatment time: 30 min). The particle size of the obtained powder is as shown in the column of Example 3 in Table 2.

  Comparative Example 4 is different from Example 3 in that the LSCF powder produced in Comparative Example 1 is used as a base particle, and SDC particles (particle size is the same as in Example 2) are mixed at a mixing ratio of 70/30 vol%. The composite treatment was performed using Nobilta manufactured by Hosokawa Micron Co., Ltd. (conditions are the same as in Example 3). The particle size of the obtained powder is as shown in the column of Comparative Example 4 in Table 2.

  Next, on one side of the 8YSZ (yttria 8% addition stabilized zirconia) solid electrolyte on which the Ni—YSZ fuel electrode is baked on the other side, the above-mentioned Examples 1-3 and Comparative Examples 1-4 are obtained. In addition, each LSCF cathode raw material powder in the form of a paste was applied by screen printing. In Example 1 and Comparative Examples 1 and 2, the baking temperature was 850 ° C., and in Examples 2 and 3 and Comparative Examples 3 and 4, the baking temperature was used. An SOFC single cell was fabricated by baking at 900 ° C. for 4 hours. Here, SDC is a difficult-to-sinter material and has an optimum baking temperature, so the baking temperatures of Examples 2 and 3 and Comparative Examples 3 and 4 containing SDC are higher than those of Example 1 and Comparative Examples 1 and 2. Is also high.

When LSCF is used as an air electrode for a zirconia-based electrolyte as described above, a high resistance substance: La ₂ Zr ₂ O ₇ , SrZrO ₃ or the like is usually generated at the interface by a reaction between the air electrode / electrolyte. In order to prevent this, a ceria-based intermediate layer is provided. However, in the present invention, an extra intermediate layer is not provided, and an LSCF having a fine and uniform structure is used, so that the interface reaction is remarkable. This is advantageous in that the electrode can be baked under low temperature conditions around 850 ° C.

For SOFC single cell of Examples and Comparative Examples thus produced, the hydrogen H ₂ as a fuel were evaluated for the cathode overvoltage (polarization voltage) of the oxidizing agent with the fuel cell characteristic evaluation apparatus as air. The cathode overvoltage was measured by the current interrupt method under the conditions of an operating temperature of 700 ° C. and a current density of 0.5 A / cm ² . The cathode overvoltage of each example and comparative example is as shown in the column of polarization voltage ηc in Tables 1 and 2.

  From Tables 1 and 2, the air electrode using the LSCF air electrode raw material powder of Example 1 has a polarization voltage as small as about ½ of that of Comparative Example 1, and has excellent air electrode performance, such as a low temperature of 700 ° C. Although suitable for operation under conditions, it can be seen that the LSCF cathode material of Comparative Example 1 has insufficient performance for low temperature operation. Similarly, the LSCF air electrode materials of the other Examples 2 and 3 have a smaller cathode overvoltage (polarization voltage) than the LSCF air electrode materials of Comparative Examples 3 and 4 and are suitable for low temperature operation. .

  This result shows that the LSCF air electrode raw material powders produced in Examples 1 to 3 are sharp with the width of the particle size distribution being limited to a predetermined range, whereas the LSCF air electrode raw materials produced in Comparative Examples 1 to 4 are sharp. The powder is caused by the broad particle size distribution and broad. That is, the LSCF air electrode raw material powders of Examples 1 to 3 have a small variation among particles, and the optimum baking temperature for each particle tends to be uniform. In other words, it is possible to set the baking temperature so as not to cause a large difference in the sintered state of each part of the electrode. On the other hand, the LSCF air electrode raw material powders of Comparative Examples 1 to 4 have a large variation between particles and a large proportion of coarse particles and fine particles. For example, when an intermediate baking temperature is set, the powder is fired inside the electrode. There are parts that become dense due to excessive sintering (parts of fine particles) and parts that are weakly sintered and weakly connected between electrolyte and cathode materials (parts of coarse particles), resulting in differences in electrode performance. it is conceivable that.

  When observing the particle state of the actual electrode, the LSCF cathode produced using the raw material powder of Example 1 shown in FIG. 4 has a uniform constituent particle size, and relatively small pore diameter and pore distribution. While it is uniform, the LSCF cathode produced using the raw material powder of Comparative Example 1 shown in FIG. 5 has a non-uniform constituent particle size and relatively nonuniform pores.

Next, the limitation on the average particle size and the particle size distribution width of the air electrode raw material powder will be specifically described. First, the air electrode raw material powder of each Example has a cumulative volume 50% equivalent diameter D ₅₀ corresponding to the average particle diameter of 0.6 μm or less as shown in the above data. Further, as the width of the particle size distribution of the air electrode raw material powder, the ratio D ₉₀ / D ₁₀ of the cumulative volume 90% equivalent diameter D ₉₀ and the cumulative volume 10% equivalent diameter D ₁₀ is limited to a value smaller than a predetermined value. Alternatively, the ratio D ₉₀ / D _{50 of} the cumulative volume 90% equivalent diameter D ₉₀ and the cumulative volume 50% equivalent diameter D ₅₀ is smaller than a predetermined value, and the cumulative volume 50% equivalent diameter D ₅₀ and the cumulative volume 10% equivalent diameter the ratio _D 50 _{/ D 10} of the D ₁₀ of which is limited to a predetermined value smaller value.

Referring to the data in Table 1 and Table 2 above, Examples 1 to 3 satisfy all the conditions of the particle size distribution, but Comparative Examples 1 to 4 do not satisfy any of the above conditions. ₉₀ / _D the predetermined value for the _10, and set to, for example, a value of around _3.7, to set the above predetermined value for D 90 _{/ D 50} and _D 50 _{/ D 10,} the value around 2.0 for example Is appropriate. In addition, each said predetermined value is changed into an appropriate value according to it, when the material composition of air electrode raw material powder differs.

  Next, when the air electrode raw material powder is formed on the electrode, the particle size distribution basically has the same tendency as the particle size distribution in the powder state. However, since fine particles (fine powder) are easy to sinter, they grow during baking, or coalesce and sinter with other particles, making it difficult to count as a single particle. Therefore, the particle size distribution in the electrode state is narrower on the small diameter side. In Examples 2 and 3 including SDC, which is a hardly sintered material, the smaller diameter side becomes wider (the lower limit value becomes smaller).

Specifically, in the case of Example 1, the average particle diameter of the constituent particles is 1.0 μm or less, and as the width of the particle size distribution, the cumulative volume 90% equivalent diameter D ₉₀ and the cumulative volume 10% equivalent diameter D ₁₀ or the ratio _D 90 _{/ D 10} of is limited to smaller ranges than the predetermined value, or the ratio _D 90 _{/ D 50} of the cumulative volume of 50% equivalent diameter _{D 50} and the cumulative volume of 90% equivalent diameter _{D 90} of less than a predetermined value Further, the ratio D ₅₀ / D ₁₀ between the cumulative volume 50% equivalent diameter D ₅₀ and the cumulative volume 10% equivalent diameter D ₁₀ is limited to a value smaller than a predetermined value. In addition, about the average particle diameter of the said constituent particle | grain, you may set a lower limit (for example, 0.3 micrometer).

Also in Examples 2 and 3, the average particle diameter of the constituent particles is 1.0 μm or less, and the width of the particle size distribution is a cumulative volume 90% equivalent diameter D ₉₀ and a cumulative volume 10% equivalent diameter D ₁₀ . The ratio D ₉₀ / D ₁₀ is limited to a range smaller than a predetermined value, or the ratio D ₉₀ / D _{50 of} the cumulative volume 90% equivalent diameter D ₉₀ and the cumulative volume 50% equivalent diameter D ₅₀ is smaller than the predetermined value, Further, the ratio D ₅₀ / D ₁₀ between the cumulative volume 50% equivalent diameter D ₅₀ and the cumulative volume 10% equivalent diameter D ₁₀ is limited to a value smaller than a predetermined value. In addition, about the average particle diameter of the said constituent particle | grain, you may set a lower limit (for example, 0.2 micrometer). Here, in Examples 2 and 3, the lower limit value of the average particle diameter is made smaller than that in Example 1 in consideration of the use of SDC, which is a hardly sintered material.

Referring to the data in Table 1, in order to satisfy all of the above particle size distribution conditions in Example 1 while not satisfying any of the above conditions in Comparative Example 1, a predetermined value for D ₉₀ / D ₁₀ Is set to a value near 3.4, for example, a predetermined value for D ₉₀ / D ₅₀ is set to a value near 1.9, for example, and a predetermined value for D ₅₀ / D ₁₀ is set to a value near 1.7, for example It is appropriate to do. In addition, when the material composition of an air electrode differs, each said predetermined value is changed into an appropriate value according to it.

When the particle size distribution is represented by volume distribution (volume basis) as described above, the cumulative volume 10% equivalent diameter D ₁₀ , the cumulative volume 50% equivalent diameter D ₅₀ , and the cumulative volume 90% equivalent diameter D ₉₀ are used as indices of the particle size distribution. Instead of using the equivalent diameter, other equivalent volume% values may be used. In addition to the volume distribution, for example, the particle size distribution may be represented by a number distribution (number basis) to limit the width of the particle size distribution.

The graph which shows the particle size distribution of the air electrode raw material powder which concerns on this invention The graph which shows the characteristic of the air electrode material which concerns on this invention Manufacturing process diagram of air electrode raw material powder, air electrode and fuel cell according to the present invention SEM photograph of air electrode produced using raw material powder of Example 1 SEM photograph of air electrode produced using raw material powder of Comparative Example 1

Claims (7)

Represented by the general formula ABO ₃ , A is composed of one or more elements selected from the group of La and rare earth elements and one or more elements selected from the group of Sr, Ca and Ba, and B is Mn, Co , Fe, Ni, and Cu are perovskite composite oxide powders made of one or more elements selected from the group consisting of an average particle size of 1 μm or less, and the width of the particle size distribution is limited within a predetermined range Air electrode raw material powder for solid oxide fuel cells. As the width of the particle size distribution, the ratio D ₉₀ / D ₁₀ of the cumulative volume 90% equivalent diameter D ₉₀ and the cumulative volume 10% equivalent diameter D ₁₀ is limited to a value smaller than a predetermined value, or the cumulative volume equivalent 90% the ratio _D 90 _{/ D 50} of the diameter _{D 90} and the cumulative 50% volume equivalent diameter _{D 50} is less than the predetermined value, and the ratio _D 50 _{/ D 10} of the cumulative volume of 50% equivalent diameter _{D 50} and 10% cumulative volume equivalent diameter _{D 10} The air electrode raw material powder for a solid oxide fuel cell according to claim 1, wherein is limited to a value smaller than a predetermined value.   The air electrode raw material powder for a solid oxide fuel cell according to claim 1 or 2, wherein the average particle size is 0.6 µm or less.   The air electrode raw material powder for a solid oxide fuel cell according to any one of claims 1 to 3, wherein at least one of a stabilized zirconia powder and a dope ceria powder is homogeneously mixed with the perovskite composite oxide powder. body.   The solid according to any one of claims 1 to 3, wherein the perovskite composite oxide powder is coated with at least one of a stabilized zirconia powder and a dope ceria powder finer than the perovskite composite oxide powder. Air electrode raw material powder for electrolyte fuel cells. It is produced by molding and firing the air electrode raw material powder according to any one of claims 1 to 5, wherein the average particle diameter of the constituent particles is 1.0 μm or less, and the cumulative volume is 90 as the width of the particle size distribution. The ratio D ₉₀ / D _{10 of the} % equivalent diameter D ₉₀ and the cumulative volume 10% equivalent diameter D ₁₀ is limited to a range smaller than a predetermined value, or the cumulative volume 90% equivalent diameter D ₉₀ and the cumulative volume 50% equivalent diameter D smaller than the ratio _D 90 _{/ D 50} is a predetermined value of _50, and the ratio _D 50 _{/ D 10} of 10% cumulative volume equivalent diameter _{D 10} and the cumulative 50% volume equivalent diameter _{D 50} is limited to a predetermined value smaller than the value Air electrode of solid oxide fuel cell. A solid oxide fuel cell, wherein the air electrode according to claim 6 is formed on one surface of a solid electrolyte, and a fuel electrode is formed on the other surface of the solid electrolyte.